Thornless Blackberry
- Current Stock:
- 0
- Other Names:
- Columbia Star, Black Diamond, Thornless Trailing Blackberry
- Latin Name:
- Rubus 'Columbia Star', Rubus 'Black Diamond'
Two of the best thornless trailing blackberries ever bred in Oregon, on one page. ‘Columbia Star’ is the newer USDA-ARS / Oregon State University release and our pick for flavor: in OSU trials it out-yielded both ‘Marion’ and ‘Black Diamond’, carried bigger berries, and scored as well as ‘Marion’ in taste tests—with no thorns at all [1]. ‘Black Diamond’ is the proven, cold-tough workhorse of Oregon’s blackberry fields, firm and reliable [1][2]. Both trace back to our native Pacific Blackberry (Rubus ursinus) and carry that rich trailing-blackberry flavor.
Note: Choose your variety from the drop-down. ‘Black Diamond’ is available only until current stock sells out. Both are self-fruitful—one plant will bear on its own. See the Comparison Table below for details.
Edible Uses
‘Columbia Star’: Large, glossy, sweet-tart berries (about 7.6 g on average—bigger than ‘Marion’) with excellent fresh flavor and top-rated purée quality. Firm enough to keep well in the fridge and freezer [1].
‘Black Diamond’: Uniform, firm, conical berries that freeze and bake beautifully; flavor is good but milder and less aromatic than ‘Marion’ or ‘Columbia Star’ [1][2].
Blackberry fruit is naturally rich in anthocyanins and other phenolics with notable antioxidant capacity [5].
Ornamental Qualities
White spring blossoms buzzing with bees, then clusters of red-to-black fruit on long, smooth canes. Trained on a simple two-wire trellis or a fence, a thornless blackberry makes a tidy, productive edible screen that kids and pets can brush past safely. Pair with Evergreen Huckleberry and Red Flowering Currant for a multi-season native edible border.
Environment and Culture
‘Columbia Star’ was bred in Corvallis by USDA-ARS and OSU and was the first true blackberry to carry the ‘Lincoln Logan’ source of thornlessness, which makes the canes completely spine-free [1][2]. ‘Black Diamond’ came from the same program (a New Zealand selection × ‘Kotata’) and became an Oregon industry favorite for its yield, firmness and cold tolerance [1][2]. Both inherit their trailing habit and deep flavor from native Rubus ursinus, a plant Indigenous communities of the Pacific Northwest continue to harvest and tend. (Learn more & how to help on our Charitable Giving page.)
Harvest, Care, and Preparation
Site & soil: Full sun; well-drained, organic-rich soil. Avoid soggy ground [3].
Training & pruning: Summer-bearing; fruit forms on second-year canes (floricanes). Tie new canes along the wires in year one; after harvest, cut out the canes that fruited and tie in next year’s [3].
Pollination: Self-fruitful; bees improve fruit set [1][3].
Cold: Both handled Oregon winters better than ‘Marion’ in OSU trials. In a December 2013 freeze, canes and buds survived about 9 °F (−13 °C) with little damage but were badly hurt near 3–4 °F (−16 °C) [1].
Harvest window (Willamette Valley): Early to late July. ‘Columbia Star’ peaks a few days ahead of ‘Marion’ and about five days ahead of ‘Black Diamond’ [1].
(See Planting Guide in next tab for more info.)
In the Kitchen
Eat them warm off the vine, freeze whole on a sheet pan for winter smoothies, or bake into cobbler and pie. ‘Columbia Star’ makes a standout jam and syrup; ‘Black Diamond’ holds its shape best in muffins and tarts.
Attributes
Type: Thornless trailing blackberry cultivars (USDA-ARS / OSU) [1][2]
Native Ancestry: Descended in part from Pacific Blackberry (Rubus ursinus) [2]
USDA Zones: ~7–9 (trailing types are the least cold-hardy blackberries; protect in cold pockets) [1][2]
Ease of Care: Easy–moderate (needs a trellis; thornless canes make training easy)
Thorns: None [1]
Light Requirements: Full sun (6–8+ hrs)
Soil Type: Well-drained loam or sandy loam; avoid waterlogging [3]
Water Requirements: Even moisture during bloom and fruit fill [3]
Pollination: Self-fruitful [1][3]
Bearing Age: Second year (fruits on second-year canes) [3]
Plant Spacing: ~3–5 ft in the row; 8–10 ft between rows [3]
Bloom Time: Spring
Harvest Time: Early–late July in the Willamette Valley [1]
Primary Uses: Fresh eating, freezing, jam, syrup, pies
Comparison Table
| Attribute | ‘Columbia Star’ | ‘Black Diamond’ |
|---|---|---|
| Yield (OSU trial avg.) | Highest: 7.5 kg / 16.5 lb per plant[1] | 4.3 kg / 9.4 lb per plant[1] |
| Berry size | 7.6 g (largest)[1] | 6.0 g[1] |
| Fresh flavor | As good as ‘Marion’; 12.7° Brix sugar[1] | Good but milder; 10.3° Brix sugar[1] |
| Firmness | Firmest of the three tested[1] | Firm[1] |
| Peak harvest (Corvallis) | ~July 12[1] | ~July 17[1] |
| Winter hardiness | Better than ‘Marion’[1] | Better than ‘Marion’; slightly the toughest in a hard freeze[1][2] |
| Thorns | Completely spine-free[1] | Thornless[2] |
| Availability | Ongoing | Until sold out |
References
[1] Finn, C.E. et al. 2014. “‘Columbia Star’ Thornless Trailing Blackberry.” HortScience (USDA-ARS / Oregon State Univ. release; yield, fruit size, flavor, ripening and winter-injury trials vs. ‘Marion’ and ‘Black Diamond’). PDF
[2] Finn, C.E. & Strik, B.C. 2016. “Blackberry production in the Pacific northwestern US.” Acta Horticulturae (cultivar histories and pedigrees; trailing blackberry cold hardiness). PDF
[3] OSU Extension — Growing Blackberries in Your Home Garden (trellis, training, pruning, spacing; self-fruitful pollination).
[4] Washington Native Plant Society — Rubus ursinus (ethnobotany).
[5] Siriwoharn, T. et al. 2004. Blackberry anthocyanins, phenolics and antioxidant properties across cultivars. J. Agric. Food Chem.
Pot Sizing Guide
Planting Guide: Thornless Blackberry — ‘Columbia Star’ & ‘Black Diamond’ (Rubus)
Tip: Two wires, full sun, steady summer water. With no thorns to fight, training and picking are a pleasure.
When Your Plant Arrives
Open the box promptly and lift your plant out gently, holding the pot rather than the stem. Leave it in its pot for now — the roots are settled and don’t need disturbing yet. Give it a slow, thorough drink until water runs through the bottom, then set it somewhere bright but sheltered, out of harsh afternoon sun, drying wind, and frost. Let it rest and acclimate there for a few days before planting. If anything doesn’t look right, please contact customer service within 7 days of delivery and we’ll take care of you.
Choosing a Site
Light: Full sun (best yields with 6–8+ hours of sun).
Soil: Well-drained loam or sandy loam enriched with compost; avoid waterlogging. Slightly acidic to neutral soils are ideal.
Space: 3–5 ft between plants on a trellis; 8–10 ft between rows.
Support: Set up a simple two-wire trellis (wires at about 3 and 5 ft) or use a sturdy fence before canes get long.
Planting Steps
Timing: Plant in early spring as soil becomes workable, or in fall where winters are mild.
Prepare: Dig a wide hole; blend native soil with compost or leaf mold for drainage and moisture retention.
Set: Plant at the same depth as in the pot; spread roots, backfill, and water deeply to settle.
Mulch: 2–3 inches of wood chips or leaves, kept a few inches off the crown.
Watering & Care
Establishment (years 0–2): Keep soil evenly moist, especially during bloom and fruit fill.
After establishment: Steady summer moisture (drip is ideal) keeps berries large and juicy.
Feeding: Top-dress with compost each spring; avoid heavy nitrogen, which pushes leaves over fruit.
Training & Pruning
This is a summer-bearing, trailing berry that fruits on second-year canes (floricanes).
- Year 1 (primocanes): Guide new canes along the trellis wires.
- Year 2 (floricanes): Fruiting side shoots develop; tie canes securely.
- After harvest: Cut the canes that fruited to the ground; keep 6–10 of the best new canes and tie them in for next year.
- Thorns: None — ‘Columbia Star’ is completely spine-free and ‘Black Diamond’ is thornless.
Pollination & Bloom
Both are self-fruitful; one plant will bear. Good bee activity improves fruit set and berry size.
Protection
Winter: Trailing berries are the least cold-hardy blackberries. Where winters dip below about 10 °F, leave new canes on the ground under mulch or row cover over winter and tie them up in late winter.
Wildlife: Birds love ripe fruit — use lightweight netting as berries color. Protect young plants from deer browse.
Airflow & sanitation: Remove spent canes and fallen fruit after harvest to limit disease.
Harvest Basics
Timeline: First real crop in the second summer after planting.
Season: Early to late July in the Willamette Valley. ‘Columbia Star’ peaks a few days before ‘Black Diamond’.
Kitchen: Chill promptly or process the same day. Excellent fresh, frozen, or cooked into jams, syrups, pies, and crisps.
PNW Notes
West of the Cascades, dry summers make mulch and drip irrigation valuable for steady fruit fill. Train canes in mild weather, when they bend easily; cold canes crack.
References
- Finn, C.E. et al. (2014). ‘Columbia Star’ Thornless Trailing Blackberry. HortScience.
- Finn, C.E. & Strik, B.C. (2016). Blackberry production in the Pacific northwestern US. Acta Horticulturae.
- OSU Extension — Growing Blackberries in Your Home Garden (training, trellis, pruning, spacing).
